1. Field of the Invention
The present invention relates to a wiper control method for vehicles, and particularly to a technique effective when applied to wiper control of vehicles equipped with an automatic wiper system.
2. Related Art Statement
In recent years, as a part of automation of on-vehicle equipment, developments have been made to a vehicle equipped with a so-called automatic wiper system which senses climate conditions and to automatically start a wiper or change the operation speed thereof. In the automatic wiper system, for example, in a car, a rain drop detector is provided at a windshield, a radiator grill, a front bumper, or the like, to sense raining conditions. In this case, particularly a detector for detecting rain drops sticking to the window shield is capable of attaining data directly relating to the view field from a driver and is therefore advantageous for control of the wiper, so that this kind of detector has come to be used in many vehicles.
Meanwhile, a wiper of a vehicle operates according to modes selected by a driver. In general, a vehicle equipped with an automatic wiper system adopts modes of "OFF", "INT (intermittent)", "LO", and "HI", and a mode of "AUTO" is added to these modes. When a driver selects the mode "AUTO", the wiper operation is controlled in accordance with a detected rain drop condition.
In this kind of automatic wiper system, however, if a drop of water sticks to a portion for sensing a rain drop when the operation mode is "AUTO", the wiper starts operating regardless of whether or not the drop of water is actually a rain drop. For example, when a vehicle is set in a car washer with the wiper'switch kept in the "AUTO" mode, the sensing portion of the system determines any drop of car-wash liquid as a "rain drop" and starts operation of the wiper. In this case, if the vehicle is washed by hands by a user or so, the wiper can be stopped by switching manually the operation mode to "OFF". However, if the vehicle is washed by a car washer, the system continues determining that the vehicle is in a rain condition and operating the wiper. Therefore, any brush of the car washer may be brought into contact with wiper arms and blades or the wiper arms may be entangled in the brush, thereby damaging the wiper.
Hence, in a vehicle mounting an automatic wiper system, various methods have conventionally been adopted to prevent troubles as described above when washing the vehicle. For example, Japanese Patent Application laid open No. 59-14563 discloses an apparatus in which wiper operation is stopped by changing a switch to a predetermined contact position when washing a vehicle. Further, in an apparatus according to Japanese Patent Application laid open No. 59-149844, the wiper is switched to intermittent operation when the rain stops and a driver is suggested shifting a switch. However, these methods carried out by a driver do not function at all if the driver forgets to operate the switch and can hardly be said to be basically effective countermeasures.
Hence, proposals have been made for a method of automatically stopping the wiper when washing a vehicle regardless of switching operation taken by a driver, and several of those proposals will be as follows. Japanese Patent Application laid open No. 60-183247 shows a method in which the wiper does not start operating until the switch is turned on again, once the rain stops. Japanese Patent Applications laid open No. 60-183248 and No. 62-189275 shows a method in which wiper operation is stopped when any rotating component of a car washer has a contact with an external switch, or when any human body or car washer comes close to or has a contact with a rainfall amount detection means.
In addition, Japanese Patent Application laid open No. 1-41446 shows a method in which the mode is switched to the "AUTO" mode only when an ignition switch is on and the driver puts on a safety seat belt. Japanese Patent Applications laid open No. 1-41447, No. 62-82865, and No. 63-28566 show a method in which opening/closing of a door is detected, and an alarm buzzer sounds or the "AUTO" mode is released if the driver goes apart from the vehicle with the mode kept in "AUTO".
Further, Japanese Patent Application laid open No. 1-285443 shows a method of inhibiting the "AUTO" mode operation when the speed of the vehicle is zero, and Japanese Patent Application laid open No. 62-163456 shows a method of preventing the wiper from operating when the parking brake is operated. In addition, as in Japanese Patent Application laid open No. 63-30260, a proposal has been made for a method of inhibiting the "AUTO" mode operation when the shift lever is at the parking position.
Although every of the methods described above includes a function of inhibiting automatic wiper operation when washing a vehicle, most of them achieve only such automatic wiper operation that is far from actual "AUTO" mode operation or are attained by sacrificing wiper operation while the vehicle is parking. These methods cannot always be practical in consideration of various situations while actual driving.
For example, in case of the method in which the switch must be reset within a predetermined period after the rain stops, the switch must be reset every time the rain starts again within the predetermined period, and this method is thus far from what the "AUTO" mode is. Meanwhile, in case of the method in which the wiper operation is stopped upon a contact with a human body or a car washer, the wiper is stopped if something has a contact even during a period when the vehicle is not subjected to car washing.
Further, in the method depending on the ignition switch and the seat belt, the wiper does not operate when the vehicle parks or stops. As for the method in which the buzzer alarms upon detection of opening/closing of a door, two different alarms may confuse each other since many types of vehicles have a function of alarming when a driver forgets to turn off headlights when a door is opened. Meanwhile, in the methods in which the wiper operation is stopped when the speed is zero or depending on the position of the parking brake or the shift lever, the wiper does not operate at the time of waiting for a signal or parking the car. In several of these methods, the wiper operation is guaranteed for a period of waiting for a signal by linking the wiper with a timer. Even in such cases, the wiper operation is stopped if the vehicle parks or stops over a predetermined time period.